While carbon dioxide (CO2) solvent is environmentally friendly and pollution-free, it has very much lower solvency than other polar solvents and has a problem in dissolving a polar compound or inactive compound. However, it has been known that a polymer of a kind of silicon like polydimethylsiloxane and a partially fluorinated compound have a good solubility for liquid carbon dioxide and supercritical carbon dioxide.
When the temperature and pressure are higher than those of a critical point, a state where densities of the two states become the same as each other and there is no distinction between the two states is referred to as a supercritical state, and is also called supercritical fluid (SCF) because the state has the characteristics of a fluid which is easy to transform unlike a solid body and freely flows.
The molecule in the supercritical state has a density close to that of liquid and a viscosity lower than that of liquid, and thus, it has properties close to gas. The molecule in the supercritical state is rapidly diffused to have high thermal conductivity, so that it can be usefully used in chemical reactions. The carbon dioxide has a low critical temperature (31.1° C.) and a low critical pressure (73.8 bar). Therefore, the carbon dioxide is able to easily reach the liquid state and the supercritical state. Also, due to the high compressibility of the carbon dioxide, the density or solvent strength of the carbon dioxide is easy to change according to the change of the pressure. The carbon dioxide is changed into gas carbon dioxide by reducing the pressure.
Also, the carbon dioxide is nonpoisonous, nonflammable, inexpensive and environmentally friendly. Under the condition of a temperature and a pressure higher than those of the critical condition (TC=31.1° C., PC=73.8 bar) of the carbon dioxide, the carbon dioxide becomes the supercritical state. The carbon dioxide in the supercritical state has unique properties different from those of the liquid or gas carbon dioxide. The supercritical carbon dioxide has a density similar to that of the liquid carbon dioxide, a viscosity as low as that of the gas carbon dioxide, and is rapidly diffused.
Meanwhile, a large number of organic or halogen solvent are annually used as a polymer polymerization solvent all over the world. All of the solvents being used are dangerous to health and safety, and are harmful to the environment. In particular, petroleum-based solvents are flammable and generate smog. When a non-volatile solvent such as an aqueous solution is used instead of the volatile solvent, wastewater is produced and there is a big disadvantage that a lot of time and energy is required for drying after cleaning.
Also, most functionalizations in the siloxane structure have been performed through POSS up to now. However, since the siloxane has a low molecular weight and has a relatively low glass transition temperature and melting point, the siloxane is not suitable for the application to the thin film within an electronic material such as OLED and organic solar cell, so that there is a problem in practicability.
As compared with an existing linear siloxane, a ladder type silicon polymer structurally secures the safety. Accordingly, the trapezoidal silicon polymer has a high thermal stability, and the use of the trapezoidal silicon polymer is expanding very rapidly due to high compatibility with the organic solvent. Also, since the improvement of characteristics of the polysilsesquioxane (PSSQ) results from a highly regular ladder-form structure, research has been variously devoted to both the development of a new starting material capable of easily forming the ladder-form structure and a method for condensing the new starting material.
Polyorganosilsesquioxane, a kind of the polyorganosilsesquioxane, is easily typically manufactured as follows. A precursor hydrolyzate is obtained by hydrolyzing trichlorosilane or rialkoxysilane, and the precursor hydrolyzate is dehydrocondensed under an alkali/acid catalyst, so that polymer having a low molecular weight (Mn is from about 20,000 to 30,000, and Mn/Mw is from about 3 to 5) can be easily manufactured.
First, a method for manufacturing the polyorganosilsesquioxane by using the trichlorosilane will be described as follows. In the hydrolysis of the trichlorosilane, oligomer (Mn is from 1,000 to 2,000, and PDI is from 2 to 5) produced by the condensation reaction performed simultaneously with the hydrolysis has a complex and various structures instead of silanetriol of a single structure, and when it becomes to have a high molecular weight by using this, it is easy to form a 3-dimensional network structure due to the structural defect (inter-hydroxy group) of the oligomer, which is caused by the existence of hydroxy group within the molecule, and any structure of its own. Therefore, the following disadvantages are caused. That is, 1) it is impossible to control the structure of the produced polymer 2) it is difficult to control the molecular weight of produced polymer and to obtain the polymer having a high molecular weight, therefore 3) the produced polymer loses high regularity, so that the solubility in the solvent is reduced 4) in particular, the low molecular weight residues have a bad influence on the thermal resistance and mechanical properties of the polymer.
Second, a prior method for manufacturing the polyorganosilsesquioxane by using the trialkoxysilane has also the advantage of being easier to handle, for example, hydrolysis rate control, than the trichlorosilane. However, due to both the molecular defect of the oligomer, which is caused by the existence of the hydroxyl group within the structure of the produced polymer, and the existence of alkoxy group, the following disadvantages are caused. That is, 1) the polymer having a branch-form instead of the ladder-form is produced 2) there are requirements for the selection and amount of the catalyst to be used, the selection of the reaction solvent, and a precise pH adjustment of the reaction solution, however, the adjustment is not easy 3) the method using the trialkoxysilane is not suitable for the manufacture of the highly regular silicon ladder-form polymer, for example, a micro gel is formed by forming a network structure which is 3-dimensional to some degree, and the like. Also, according to both various synthesis methods known up to now, for example, a sol-gel method, a ring opening polymerization method, an equilibrium polymerization method, etc., and what is known through the research on their structures, the condensation process is very complex and various and the structure of the polymer is not sufficiently controlled, so that products now being marketed does not comply with various conditions for being used as industrial new material. This problem acts as a certain limit to practicalization.
In the publication of Korean patent application No. 10-2009-0056901, disclosed is a polyalkylsilsesquioxane particle and a method for manufacturing the same. More specifically, the patent application provides a method for manufacturing the polyalkylsilsesquioxane through the first reaction in which, after an acid homogeneous aqueous solution is prepared by adding an acid catalyst to an aqueous medium, the hydrolysis is performed by adding alkyltrialkoxysilane to the aqueous solution, the second reaction in which a polycondensation is performed under an alkali catalyst, and the third reaction in which end-capping is performed by adding alkoxytrialkylsilane including triorganosilyl group, and provides the polyalkylsilsesquioxane particle manufactured by the method. According to the invention, by adding diol having 3 or more than carbon atoms before supplying the alkyltrialkoxysilane, polyalkylsilsesquioxane particle can be obtained which has a large diameter and a narrow distribution of particle sizes, while maintaining the property equal to or greater than the existing property. However, since the final result is limited to the polyalkylsilsesquioxane and the acid catalyst is used, the range is limited. Also, there are requirements for the selection and amount of the catalyst to be used, the selection of the reaction solvent, and a precise pH adjustment of the reaction solution, however, the adjustment is not easy. Further, there still remains a problem that the produced polymer loses high regularity, so that the solubility in the solvent is reduced. In particular, the invention does not disclose the structure and shape of the final result, so that structural stability is not obtained.